This proposal examines the hypothesis that functional defects in myocytes from hearts of cardiomyopathic and spontaneously hypertensive animals can be traced to changes within the myocyte itself. Furthermore, it is hypothesized that when cells from animals with inherited abnormalities are challenged with a stress, they will be incapable of responding similar to cells from control animals. These hypotheses will be tested in cell culture and investigated in terms of contractile and stress protein synthesis and mRNA expression in neonatal myocytes from hearts of animals with the inherited abnormalities. The basic strategy will be to establish neonatal cardiac myocytes in culture, extensively characterize their growth under basal conditions and then determine their response to stress. The use of cell culture will allow us to examine the intrinsic nature of the cardiac myocyte devoid of systemic influences. To accomplish this, cells in culture from normal and abnormal hearts will be compared concerning: 1) their growth and differentiation, and 2) their response to environmental stress (elevated temperature, hypoxia, and catecholamine stimulation). This will be examined in the total cellular population using native and two-dimensional gel electrophoresis, dot blotting and Northern analysis. At the single cell level immunofluorescence and in situ hybridization techniques will be used to examine cellular heterogeneity in terms of myosin and actin isoforms and the "HSP" 70 proteins. We will investigate the expression of the HSP70 proteins under both basal and stress conditions and also examine the presence of message for "HSP" 70 following imposition of a stress. By examining two different disease models in culture at the cellular and molecular levels under basal and stress conditions, we will gain a better understanding of the etiology of two heart defects which result in cardiac hypertrophy. By using cell culture techniques we will be able to investigate these processes without the complications of hemodynamic load or secondary abnormalities.